Studies that examine #change in the #population of flora and fauna often do so against a baseline of relatively recent distribution data. It is much rarer to see evaluations of population change over the longer–term in order to extend the baseline back in time. Authors used two methods (regression analysis and line of equality) to identify long-term differences in abundance derived from qualitative descriptions, and we test the efficacy of this approach by comparison with contemporary data.
Descriptions of bird population abundance in Cambridgeshire, UK, from the first half of the 19th century were used and compared with more recent estimates by converting qualitative descriptions to an ordinal scale. Authors show, first, that the ordinal scale of abundance corresponds well to quantitative estimates of density and range size based on current data, and, second, that the two methods of comparison revealed both increases and declines in species, some of which were consistent using both approaches but others showed differing responses. Study also show that the regional rates of extinction (extirpation) for birds are twice as high as equivalent rates for plants.
McCollin, D., Preece, R. & Sparks, T. (2015). Pushing back the baseline: a novel approach to detect long-term changes in terrestrial faunal abundance using historical qualitative descriptions. European Journal of Ecology, 1(1), pp. 32-42. doi:10.1515/eje-2015-0005
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